So as I eagerly await my copy of Art and Academe, I was combing the archives for dribs and drabs of the treasures within, and saw the suggestion that, if you're going to allow Hermetic breakthroughs to create new arts, then there should be 7 techniques and 12 forms, for aesthetic reasons. The biggest problem in this is the forms, each new form creates a hole in a magus' magic resistance that he needs to waste seasons of study covering, and having more techniques to spread his xp between isn't very exciting either. A mystery cult using a Form that can punch through a magus' magic resistance may find that some consider stamping them out easier than learning the form to defend themselves.
If you want a stupidly vast Hermetic Breakthrough that (almost) all magi will seek out hungrily to increase their own power, reduce the number of Arts they have to split their power between. 4/9/13 is a perfectly magical set of numbers as a goal.
I toyed with a drastic reworking of all arts except aq/au/ig/te (those four seem inseparable and unassailable), but it didn't work out. After much consideration, I feel Mentem is the form most ripe for dissection ("Milord! The Mentem masters are attacking!" "Release the magical beasts, they're immune to their powers.")
First, those spells that affect ghosts and spirits get moved to Vim.
Second, those spells which can be effected by altering the humors of the body, such as Rising Ire, or Pains of Perpetual Worry, get moved to Corpus.
Third, those spells that affect language, the memory, and the imagination, get moved to Imaginem. ("Milord, Jerbiton has come to assist!" "Exactly as planned.") Frosty Breath of the Spoken Lie ends up here, because while animals can deceive, only the gift of language allows a person to lie.
Fourth, Imaginem gets renamed to represent its broader power.
I'm honestly not sure what to do with the "Transparent Motive" and "Conflicting Motive" spells.
There's a hole here, which creates a new Lesser Limit, the Limit of Free Will, that supersedes the Limit of True Feeling. You can overwhelm a person with emotion, you can numb his will, you can make him forget all his allies, and you can make him believe you are the only trustworthy person in a world of liars, but at the end of the day he has free will and makes his own decisions as to what to do. The only spell in the core book this affects directly is Enslave the Mortal Mind.
(As an aside, in the new system, I think Weight of a Thousand Hells and Visions of Infernal Terrors should be renamed, because they sort of impinge on a person's ability to choose between good and evil. As "Shackles of Despair" and "Curse of Unknown Horrors" they make decent Corpus and Imaginem spells under the new scheme.)
The Techniques are a lot harder. The more I try to stuff them into 4 arts, the more I end up with one or two arts superior to the others. Ironically, I can fit them into three arts relatively cleanly:
A positive art (Succuro, bless, weal), containing all of Creo and those aspects of Muto that could be considered blessings.
A negative art (Vulnero, curse, woe), containing all of Perdo and those aspects of Muto that could be considered curses.
("Oh no! The Muto masters have arrived!" "Hold them off, lackey, the great work is almost complete.")
The separation between these two is sometimes story-driven. Prime example, the spells Beast of Outlandish Size and Beast of Miniscule Proportions. There are plenty of negatives to being huge, and plenty of positives to being small, but at the end of the day Outlandish Size says, "the new beast... looks much more impressive," and Miniscule Proportions says, "the beast appears to be the runt of the litter," making the first a positive, and the second a negative.
Finally, a "communicative" art that lets you ask questions (intellego) and give orders (rego). I know this looks like I just threw the last two arts together and came up with a justification for it, but at first I was really resistant. Intellego looked unassailable as an independent art. The inspiration for this was seeing Ware in the unified virtue/flaw index, and, not actually owning RoP:F, I started wondering what it could do, and considered the different words derivative of Ware... aware, of course, but also beware, which seemed to unite it with warding, a Rego function, and suddenly it made more sense than I was originally ready to give it credit for.
A few guidelines may find themselves orphaned. That is, there might be a rego guideline that now makes more sense as either a positive or negative guideline.
But that's 3/9/12, which I do not consider magically stable (trust me on this, I'm not just the president, I'm also a client.) If only there were one more art I could throw in... I'll spare you all the ideas I had, and give you my final result: Every mage gets a free major magical focus, in addition to their other virtues and flaws. This is their "Thirteenth Art" on which all their other arts depend. This has these benefits:
A. Being a major virtue, it is sympathetic with the Techniques, creating a 1/3/4/9/12/13 scheme that is very magical.
B. It resolves a personal crisis of mine. Whenever I read a book about anything magical that doesn't have to do with the Order, (Hedge Magic, Rival Magic, the Divine... I'm still obsessed with making something out of Ars Notoria) it reads like a menu of ideas for magical powers, and I just bubble over with plans. But when I read the main book, it's like looking in a refrigerator. All the ingredients are there, but I don't know what to make. A book like the Mysteries is more like a spice rack than a recipe book. The three Houses of Hermes books were really my savior in this regard, but... moving on. By forcing every character to decide first, "What is my major magical focus?" the rest of character creation becomes much easier. If nothing else, you can make your Major Magical Focus a copy of something you read in one of the other books, "Oh! Oh! I'll be a hermetic philosophic elementalist!"
I realize this is all possible already without handing out a free virtue, but it's sorta buried in the back of the fridge next to the vegetable dip, which is kind of a barrier for idiots like me who can't think outside the box. This would be an interesting Breakthrough all by itself, turning the granting of an arbitrary Major Magical Focus, chosen by the recipient, into a Mystery that is initiated at the end of apprencticeship, using the Gauntlet and the Oath as an ordeal.
C. It introduces some exciting new hermetic virtues and flaws. Of course there's "Weak Focus," which turns your major magical focus into a minor magical focus, or "Empty Focus," which means you have no focus at all (Meaning that becoming a generalist is a conscious choice). At first I thought this would defeat the purpose of having a free focus, but then I realized that the flaw occupies 3 of your 10 flaw points, and the virtue you replace it with takes up 3 of your virtue points, so it's not a perfectly even trade, which made me happy.
More importantly, there's "Puissant focus," which would allow your focus to cover an even broader area than a regular major magical focus. For example, "All those abilities formerly covered by the Mentem form," or "All those abilities formerly covered by the Muto technique." ("Milord, strange news!" "Yes, lackey, I know.")
The real problem with all this is it is much too much. My players would never commit to a saga that long. Heck, I'll probably vanish from the forums here as soon as some other system takes their fancy. But as a mental exercise it has amused me for several hours, which makes the price of the books all worthwhile. I'm hoping to share some of that amusement with you.
PS: Some spell guidelines may need to be adjusted for balance reasons. cough ¬.¬